Field of the Invention
The present invention relates to a toner for use in electrophotographic methods, electrostatic recording methods, magnetic recording methods and the like.
Description of the Related Art
Increased print speeds, energy efficiency and space saving are conventional demands made of laser beam printers (LBP).
Because the time spent passing through the fixing unit is shorter at faster print speeds, the amount of heat received by the toner is less even if the temperature setting of the fixing unit is the same. Lower temperature settings are also desirable from the standpoint of energy savings, and thus there is a demand for toners with good low-temperature fixability.
To improve low-temperature fixability, the toner is preferably sharp-melted within the fixing nip, and design features such as softer binder resins are desirable for this purpose.
However, it is known that when measures are taken to improve the low-temperature fixability of the toner, discharge adhesion of the printed image becomes a problem.
Discharge adhesion here means that when consecutively printed images accumulate in the printer output tray, the images stick together because they are stacked while still hot, and image defects then occur when the adhering images are pulled apart.
Discharge adhesion is especially likely during double-sided continuous printing because there is more heat accumulation on the fixed paper, and the sheets are stacked while still hot. Double-sided printing has become more common recently as a way of effectively using paper resources in the office, and further improvements are needed.
Fixed papers are also more likely than in the past to accumulate without time to cool due to recent increases in printer speed, so discharge adhesion is highly likely under current conditions.
One possible method of solving the problem of discharge adhesion is to promote cooling of the fixed paper by installing several cooling fans in the main printer unit. However, such methods may pose problems in terms of energy savings and printer size.
Thus, despite demand for toners with both low-temperature fixability and low discharge adhesion, there remains room for improvement.
Japanese Patent Application Publication No. 2007-86459 describes a toner in which both low-temperature fixability and hot offset resistance are achieved by functional separation, by including a linear component soluble in organic solvents (soluble component) and a crosslinked component insoluble in organic solvents (insoluble component) in the toner.
Japanese Patent Application Publication No. 2015-52697 describes a toner in which both low-temperature fixability and heat-resistant storability are achieved by designing both the toner itself and a tetrahydrofuran-insoluble matter in the toner with low glass transition temperatures, and by forming a shell of a resin fine particle with a high glass transition temperature on the toner surface.